Process of making acetic anhydrid.



UNITED STATES PATENT OFFICE.

HENRY DBEYFUS, OF BASEL, SWITZERLAND rnocnss or MAKING ACE-TIC mmroam No Drawing.

To all whom it may r'oneern:

lie it. known that I, Haney Dam'ros, a citizen of the Republic of Switzerland, residing in liasei, Switzerland, have invented new and useful improvements iIi'PIOGESSGS of Making Aeetic Anhydrid.

The present invention relates to improvements in the manutaeture of acetic anhydrid and has for its object to provide a. process \\l1tl(l) the manufacture of acetic anhydrid can he materially simplified, and a very pure product produced with a high yield.

in my French Patent 478951, 1 have d scribed the manufacture of acetic anhydrid, using llj'lUF-Xiilftlttt, obtained for example by heating s dium hi:-uifate inv eurruo.

in French Patent H8342 of September it 15112 and in its addition 1767 1 of April lh. 1913. t have proposed toananut'aoture aetie anhydrid or otht anhydrids of acids ot the fatty htiieh by causing acetate of sodium ol' other salts of the fatty acids to re act with :ailt'urie anhydrid alone or mixed with sulfurie acid or chlorosulfonio acid, \vhile c oling the reaetion mixture, comprising for example sodium acetate, before the iliiltltttlt'tltlfi of the sulfurie anhydrid or mixture oi sulfuric anhydrid and sulfuric acid or ehlorosulfonio avid.

Ata-ording to the present invention a sad of at'etie aeid. such as acetate of sodium or of calcium, is caused to react. with sulfuric. anhydrid, or sulfurie auhydrid mixed with. sull'uric acid or chlorosulionie acid. this re aetion for the formation of aeetie anhydzid being carried out in the presence of a diluentor such as aeeti anhydrid or acetic acid, and the reaction mixture being cooled to low temperature, 5. 0., below 5 (1. and preferahly below U (1., throughout the reaction.

When the ,reaction is complete. the acetic anhydrid formed can he distilled off, preforalily in *vacuo.

The employment of a diluent is essential, for I have found, especially for the manutaetnre on a large seale, that unless a diluent is en'iployed it is not possible without using very complicaied apparatus, to hold the temp rature sufiioiently low, to avoid decompoition of considerable of the acetic acid radical. liven if the sulfuric anhydrid or mixture thereof with sulfuric or chlorosulfonic acid is introdueed in very small amounts at a time. there is liable to be developed a consideralile local overheatin causing local. dtaromposilion ot' the acetic anhydrid and Specification of; Letters Patent.

Patented ()et. 29. 19W

reaction between the produeta of smlt u composition and sulfurie acid eom iou leading to the produetion of sulfur or otlo IllOtillti'BOf decomposition ditiieult to i=- move from the acetic al'ihydrid. Such a t" cal decomposition also eausea a. consider-al decrease in the yield of aeetie anhydrid Without using a diluent it is not pos -il l to obtain a homogeneous mixture. so that th' yield would also sufler from this eause.

Also it is essential that a low teinperatuu.

he maintained as before mentioned tlnouel out. the reaction.

it. is also necessary that when einplovinp aetie anl't vdrid or :ltft'litf acid an diiuent. the sait of acetic a id halt he on em ieet'ore th sulfurie anhydrid i""! lit1i(".1 i? he intro dared. for it the a ti" anlnuiiid o ttllth' acid were to remain even Fern -sh rt t Contact with the suilnrie anhvdrid, e position would occur, even at ioiv tenniera ture resulting in the formation of sulto aeetic acid and involving, during the suhse quent distitling oti of the aeetie anlivdrid, a deeomporntrun develop ng sulFui' and other product which \vonhi not out}: len er the aeetio anhydrid impure, but avoid .ifso di' Ininish the yield oi" acetic anhvdrid.

Thus in every case, and during the entire period of reaction lie-tween the suitor-it anhydrid and the aeetate, the diiuent must be present and the tenua-i'atiu'e must he kept belou 5" C.

In producing the re. .tioi hetween the sulforte :lnhethid and the dry titetitit, the ma.- terials slwtlld he enig ot'ed in ahe the theoretically et'lnii'aient :iuantities. it being noted that one moleeule of S0,, eorrespondd to two mo eeules of sodium acetate or one molecule of ealeiuni acetate. 'lhus with sodium acetate the'proju'n-tions for the leaetiou are taken in accordance with the equation.

In earnvingout this proeess the sulfuric anhydrid is added to the acetate mixed with the diluent such as aeetie anhydrid or a etic aeid, cooling the mass throughout the reartion to maintain it helon' 5 t. and lli'tfBlably below 0 (L, and agitating.

After the reaction has been ttml ileted, the acetic anhydrid ean he distilled o. preferably in 'uac'uo.

\Vhen mixtures of sulfurie anhvdrid and sulfuric acid are employed I may use miX- tun: containing for example, from 50 to 701 more or less, of free sulfuric anhydrid.

I claim- 1. A process for the manufacture of acetic anhydrid which comprises causing \uliuric, anlrrdrid to react with a dry salt of are! it acid in presence of a liquid diluent inapable of reacting with acetic anhydl'id and maintaining the temperature below 5 C. throughout the reaction.

2. A process for the manufacture of acetic anhydrid which comprism raining sulfuric anliyllrid to react with a dry salt of acetic acid in presence of a liquid diluent incapable of rcactiin; with acciic anhydrid and maintaining the temperature below througlr out the reaction.

A prove for the nuinufaciure of :i cii :inhydrid which comprisc causing imi l ztltltj lllli to rea t with a dry salt of '1 a i i in pi'ewncc ol' lltilllti art-ticanhy- .1, 'wl nd nmintaining the temperature bel-w v tlu'o glioui the rea tion.

l pr nt for the manufacture of t .t \'il' i lii li t t|li?i'l ih calming ullu ii lllll jtll i l to rent-t with dry sodium i iit i Ii: prcwnce of a liquid diluent inagni l of reacting with acct iv ai'iliyd rid and maintaining the temperature below 5 C. throughout the reaction.

5. A process for the manufacture of acetic illlll Ytll'ltl which comprises causing sulfuric anhydrid to react with dr i sodium acetate in presence ofa liquid diluent incapable of reacting with acetic anhydrid and maintaining the temperature below 0 F. throu hout the reaction.

(1. i process for the nnmufaeture of acetic anhrdrid, which comprises causing: sulfuric auhydrid mixed with sulfuric acid to react with a dry acetate in prewnre of a liquid diluent incapable of reacting-- with acetic anlrrdrid, andmaintaining the, tear perature below 5 C. throughout the reactlon.

7. A process for the nuinufacture of acetic anhydrid, which C(llllpl'ihifi causing sulfuric anhydrid mixed with sulfuric acid in a proportion of between and free anhydrid. to react with a dr acotate in pl'e,5 once of a liquid diluent incapable of reacting with acetic anhydrid and maintaining the temperature below 0 throughout the reaction.

In testimony I have hereunto subscribed my name.

HEJRY DRICYFUS. \Vitnesses:

FREDERU'K AL'uENJgAi n, ARNOLD ZUBER. 

